Chrome Version: 72.0.3595.2
OS: Win 10
Device: Oculus, Vive, Windows Mixed Reality

What steps will reproduce the problem?
(1) Connect a Vive headset to the computer.
(2) Verify Steam VR is running and headset is detected.
(3) (I think this step is optional) Go to a WebXR site and press enter VR. E.g. https://immersive-web.github.io/webxr-samples/positional-audio.html
(4) Unplug the Vive headset from the computer.
(5) Plug the Windows Mixed Reality headset into the computer.

What is the expected result? Steam and Chrome should be ready and able to start a VR presentation with the newly plugged in Windows Mixed Reality headset.

What happens instead? Steam VR shows a couple error msgs in red; 'Not Ready', and 'Headset not tracking'. Chrome still looks like it's in VR, there's still and exit VR button (Chrome not exiting a presentation is a separate issue; bug 902382).